Identifying key words can inform your understanding of the author’s motivation and message.
Look for patterns in the use of certain words and phrases. Are they frequently repeated? Do they have a certain connotation? Is the author trying to tell us something by his choice of these words?
For example, in John’s gospel ‘the world’ is always a bad place; 'light' is always positive; 'darkness' is always negative; 'signs' are miracles; and ‘the Jews’ are typically Jewish leaders opposed to Jesus.
In John’s epistles take note of words like ‘love’ and ‘children.’